1. Field of the Invention
The present invention relates to detection of a short circuit fault in a motor control device that drives a plurality of motors.
2. Description of the Related Art
There is known, as a fault detection technology for a motor drive system, for example, as disclosed in JP 06-233450 A, one in which a current detection resistor is placed on a DC bus line at each of a positive terminal side and a negative terminal side of an electric power converter that drives a motor, and when an overcurrent is detected by the current detection resistor, it is determined that a short circuit fault occurs.
When the conventional fault detection technology for the motor drive system is used in a motor control device that drives a plurality of motors, there arises such a problem that two current detection resistors are necessary for one electric power converter, resulting in an increase in cost.
Further, a current that flows in the DC bus line flows in synchronism with an on-timing of a switching element of the electric power converter. For that reason, in the case of detecting the current flowing in a current detection resistor which is arranged on the DC bus line by a microcomputer, there is a necessity of implementing A/D conversion in synchronism with the on-timing of the switching element of the electric power converter. In order to perform the A/D conversion in synchronism with the on-timing of the switching element in the manner described above, it is necessary to use the microcomputer with a high-precision timer, leading to a problem of high cost.